1. Field of the Invention
This invention relates to a music system, a tone generator, and a musical tone-synthesizing method, which reproduce waveform data.
2. Prior Art
Conventionally, a music system is known, which reads out waveform data stored in a hard disk or a floppy disk, and generates musical tones based on the waveform data. The conventional music system is comprised of a host system formed by an ordinary personal computer or the like, which is equipped with an external memory device such as a hard disk, and a subsystem having a sound board connected to the host system via a predetermined interface. The host system operates on a program stored in a program memory to read waveform data (PCM data) to be reproduced over a long time period, from a hard disk or a floppy disk as the external memory device, and sends the read waveform data to the sound board of the subsystem.
On the other hand, the sound board once stores the wave data supplied from the host system in a RAM, reads the waveform data from the RAM to form musical tone data by means of a tone generator LSI, and converts the musical tone data to an analog signal by means of a D/A converter, which is then sounded by a sound system formed of an amplifier, a loudspeaker, etc.
In the conventional computer music system described above, however, the amount of waveform data which can be reproduced at one time by the sound board, i.e. the reproduction time period for reproducing musical tones depends upon a writing time period required for waveform data transferred from the host system to be written into the RAM of the sound board, the memory capacity of the RAM, and a reproduction time period required for reading the waveform data from the RAM and generating musical tones.
Therefore, for example, as disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 5-66777 and its corresponding U.S. Pat. No. 5,321,198, a RAM is employed as a waveform memory, which has two divided memory areas to serve as a double buffer such that while one piece of waveform data is being read from the RAM for reproduction, another piece of waveform data is written into the RAM. By repeating this reading and writing operation, any long piece of waveform data can be reproduced. A music system according to these publication has an exclusive host system or subsystem which has a much shorter writing time period than a reproduction time period thereof.
Thus, the system according to U.S. Pat. No. 5,321,198, etc. having a much shorter writing time period than the reproduction time period can thus reproduce any long piece of waveform data without a limitation on the reproduction time period. On the other hand, however, if the host system is formed by a general-purpose personal computer, or if the subsystem uses a tone generator formed by a general purpose sound board, a RAM used in the sound board sometimes has a small memory capacity or a long writing time period required for waveform data to be written into the RAM, compared with a reproduction time period thereof. In such a case, waveform data cannot always be reproduced without a limitation on the reproduction time period. Thus, even if the same writing and reading method as disclosed in the above publications is employed, depending upon the construction of the music system or the capacity of the subsystem, the amount of waveform which can be reproduced at one time, i.e. the reproduction time period for reproducing musical tones is limited.